Translesion DNA synthesis polymerases (TLS pols) are vital to bypass and tolerance of DNA damage. The mis-regulation of TLS pols occurs in many types of cancer, including malignant brain tumors of glial origin. Human DNA polymerase kappa (hpol ?) was recently shown to be an independent prognostic indicator of poor outcome in glioma patients. However, the mechanism(s) leading to up-regulation of hpol ? in gliomas and the precise effects upon DNA replication remain unknown. The experiments outlined herein will examine whether tumor-promoting activation of the aryl hydrocarbon receptor (AhR) leads to constitutive up-regulation of hpol ? in gliomas and then investigate mechanistic features associated with hpol ? activity in these deadly tumors. The central objectives include investigating mechanisms that promote hpol ? over-expression in glioma cells, determining the effect of this mis-regulation upon replication stress responses, studying protein-protein interactions that alter hpol ? activity and examining potential ways of improving glioma treatment through targeted inhibition of TLS pols in brain tumors. The current proposal will address important questions, such as: 1) Does the AhR pathway regulate hpol ? in gliomas? 2) Do exogenous or endogenous AhR ligands affect hpol ? expression and/or activity? 3) How does blocking endogenous AhR-signaling in gliomas affect replication stress? 4) Can modulation of TLS activity in gliomas potentiate anti-cancer treatments? 5) Do protein-protein interactions between hpol ? and the genomic caretaker Werner's syndrome protein (WRN) limit mutagenic bypass of DNA damage in glioma cells? The experimental strategies utilize in vitro cell culture, mutagenesis assays, structure-function analyses, small-molecule inhibitor studies and proteomics to ascertain the role of hpol ? in gliomas. The long-term goal of the application is to produce models for replication stress and TLS activity that inform our understanding of genomic maintenance and mutagenesis in gliomas, while also providing insights into how we might better treat patients suffering from this disease. The conclusions derived from these studies will dramatically improve our fundamental definition of processes that occur in malignant brain tumors, a major public health concern.